Mobile devices with various methods of connectivity are now for many people becoming the primary gateway to the internet and also a major storage point for personal information. This is in addition to the normal range of personal computers and furthermore sensor devices plus internet based providers. Combining these devices together and lately the applications and the information stored by those applications is a major challenge of interoperability. This is achieved through numerous, individual and personal information spaces in which persons, groups of persons, etc. can place, share, interact and manipulate webs of information with their own locally agreed semantics without necessarily conforming to an unobtainable, global whole. These information spaces, often referred to as smart spaces, are extensions of the ‘Giant Global Graph’ in which one can apply semantics and reasoning at a local level.
Each information space entity can be considered as an aggregated information set from different sources. This multi-sourcing offers considerable flexibility by enabling the same piece of information to come from different sources. Furthermore, in an information space, information requested by a user may be distributed over several information sets, and therefore in order to deduce an accurate answer to a request, there is the need for extracting (e.g., projecting) or combining (e.g., injecting) the information from different sources into a new information space. However, as the number of queries and resulting information spaces increases, the challenge of keeping track of the combined and/or extracted information among the various information spaces also increases.